Traditionally, chlorofluorocarbons (CFCs) like trichlorofluoromethane and dichlorodifluoromethane have been used as refrigerants, blowing agents and diluents for gaseous sterilization. In recent years there has been universal concern that completely halogenated chlorofluorocarbons might be detrimental to the earth's ozone layer. Therefore, stratospherically safer alternatives to these materials are desirable. Consequently, there is a worldwide effort to use fluorine-substituted hydrocarbons which contain fewer or no chlorine substituents. The production of HFC's, i.e. compounds containing only carbon, hydrogen and fluorine has been the subject of interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. It is known in the art to produce fluorocarbons such as HFC's by reacting hydrogen fluoride with various hydrochlorocarbon compounds. Such HFC's are not only considered to be much more environmentally advantageous than hydrochlorofluorocarbons (HCFC's) or chlorofluorocarbons (CFC's) because they are not non-ozone depleting, but also they are non-flammable, and non-toxic as compared to the chlorine containing compounds.
HFO-1234ze(E) is also known as trans-1,3,3,3-tetrafluoropropene, which is Honeywell's new low global warming potential (GWP), fourth generation blowing agent and propellant. This low GWP molecule is the first hydrofluoroolefin (HFO) to be commercialized into these industries. This molecule has low environmental impact, as measured by its ultra-low global warming potential and zero ozone depletion potential (ODP). HFO-1234ze(E) blowing agent is fully compliant with the European Union's F-Gas regulation. As a gas material at room temperature, this molecule has diverse applications including as a blowing agent for polyurethanes, polystyrene and other polymers; as well as an aerosol propellant.
US Patent Publication No. 20080051611 provides a process in which 1,1,1,3,3-pentafluoropropane (HFC-245fa) is converted into trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)). The HFC-245fa is dehydrofluorinated to produce a mixture of HFO-1234ze(E), cis-1,3,3,3-tetrafluoropropene (HFO-1234ze(Z)), HFC-245fa and hydrogen fluoride (HF). HFO-1234ze(E) has been disclosed as a useful blowing agent in one component foams.
It has now been found that an important intermediate in the production of substantially pure HFO-1234ze(E), are the azeotropic or azeotrope-like compositions of HFO-1234ze(E)/HFO-1234ze(Z)/HF, HFO-1234ze(E)/HFC-245fa/HF and HFO-1234ze(Z)/HFC-245fa/HF. These intermediates, once formed, may thereafter be separated into its component parts by known extraction techniques. The azeotropic and azeotrope-like compositions find use not only as intermediates in the production of HFO-1234ze(E), but they are additionally useful as nonaqueous etchant mixtures for etching semiconductors in the electronics industry, as well as compositions for removing surface oxidation from metals. These ternary azeotrope or azeotrope-like compositions are then available for separation into their component parts.